Construction mixtures like mortar, screed compositions, plaster, construction adhesive, etc., besides containing binders like cement, lime, or gypsum, and aggregates like sand or rock meal, usually also contain additives like water repellents, water retention agents, retarders, accelerators, air entraining agents, liquefiers, etc.
The quantities of these individual additives in the overall mixture are usually under 1 wt. %, often even below 0.1 wt. %. The agents differ in their physical properties, and often are quite strikingly different from the other components of the binder mixture, i.e., they sometimes have a much lower specific gravity or a lower bulk weight or they are present as a liquid. These properties make it hard to distribute the additives optimally in the binder mixture. For example, the physical mixture of various small amounts of very light powders with large amounts of relatively heavy components, as are present in the binders and aggregates, presents great problems and requires a lot of mixing expense. On the other hand, liquid additives can result in clumping or, if they are dissolved in water, hardening of the binder.
The homogenous mixing in of additives or supplementary agents therefore requires a very high expenditure of equipment and machinery. The high effectiveness of these additives--documented, for example, by the use of a quantity of as little as 0.05 wt. %--does not allow fluctuation in concentration of these agents. Therefore, one possible solution is to add them not in pure form, but as "diluted" material, disposed on a carrier.
Thus, EP-A-0 409 774 describes a mixture of lignosulfates and polyphosphates, as well as a processing agent, which is suitable as a retarder system for hydraulically hardening cements. A mineral component, such as vermiculite, perlite, bentonite or montmorillonite, in an added amount of around 30-60 wt. %, is also used as an aggregate. This mineral component has the property of adsorbing water and swelling. No other effects are observed or specified.
JP-A-61 006 164 describes a granulate that contains 20-90 wt. % of a supplementary agent (a melamine sulfonate-formaldehyde condensate), which has been produced with 10-80 wt. % bentonite as a pelleting agent.
The homogeneous mixing in of liquid additives is also a problem. Liquids are frequently converted to a powder-like, pourable form, in order to facilitate such mixing. There is the known use of pyrogenic silicas, which are suitable for "solidification" of liquids by virtue of their high specific surface and their large pore volume. But these carrier materials have the disadvantage of contributing nothing to the binder system and being present as inert fillers.
Wall sealing compounds are known from DE-A-3 610 755, which contain clay minerals with layer lattice structure that are capable of swelling, such as bentonites and montmorillonites. These are preferably used in the form of sodium bentonite, which has large swelling capacity. The clay minerals are the main ingredients and not a supplementary agent for the wall sealing compounds.
A dry mixture is known from DE-C-4 205 354 for the production of construction material suspensions that can be hydromechanically delivered. This mixture contains as a primary ingredients 10-80 parts by weight of a hydraulic binder based on cement clinker, 10-80 parts by weight of filter ash from coal furnaces, and 1-20 parts by weight of swellable clays. Highly swellable clays are preferred.
A binder mixture is known from DE-C-4 213 348 for the single-step production of sealing walls, containing as the primary ingredients 30-82.7% by mass of foundry sand, 2.0-1.0% by mass of a hydroxyl-ion-forming seed ingredient, and 15-65.0% by mass of clay minerals. Thus, the clay minerals are present in a very high proportion. Nothing is said about their swelling ability.
A coating composition for masonry is known from DE-A-2 715 305, containing a carrier material component and a pigment-extender-component, being characterized in that it contains a smectite clay and a water soluble polymer. The smectite clay is preferably present in a quantity of around 2-5 wt. %. There is no information about the swelling capacity of the smectite clay.
A process for the production of frost-resistant mortar and concrete is known from DE-B-1 082 544, in which air pore forming agents and finely pulverized adsorbents such as silica and aluminum compounds, e.g., zeolites, permutites, bentonite, kaolin, aluminum oxide, or active silicic acid are added to the mortar or the concrete or the components thereof. These additives are supposed to increase the frost resistance by acting on the air pore forming agents. There is no information on the swelling capacity of the adsorbent.
DE-C-736 842 and DE-C-764 999 disclose a method for hardening and tempering mortar and concrete, being characterized in that, before or during the processing of the mortar and concrete materials, water-soluble lignin derivates, as well as kieselguhr or other surface-active silicas and/or corresponding silicates (e.g., bentonite) are added. The last-mentioned additives are supposed to increase the compressive strength of the concrete and reduce the water permeability, supposedly because of a large specific surface. There is no mention of the swelling capacity of the additives.
DE-C-576 766 concerns a method of production of colored plaster mortars, in which colored, colloidally dispersible, natural or artificial silica gels in powder form are added to high-boiling organic compounds. In the case of bentonite which is used as an example, the bentonite is an acid-activated kind, since natural or alkaline activated bentonite contains no silica gel.
AT-A-280 134 concerns a mortar or concrete additive, which consists of a mixture of bentonite and air-introducing and/or plasticizing agents. The swelling ability of the bentonite is not indicated.
An insulating mixture based on cement and sand is known from AT-A-268 132 (equivalent to CH-A-459 858), which contains, as an additive, an activated alkali bentonite with a swelling ability of up to 1000% in a quantity of up to 15 wt. %, as well as another component with hydraulic properties like cement, preferably fly ash, as well as surface-active substances and familiar quick-setting agents. The use of highly swelling alkali bentonites in large quantities, however, causes formation of dry cracks.
A surface-active cement supplementing agent is known from CH-A-463 357, which contains finely divided, solid, natural or synthetic, inorganic, oxygen-containing silicon compounds with a coating of finely divided, surface-active, nonionic addition products of ethylene oxide.
The use of highly swelling bentonite suspensions in conjunction with cement is known from the company literature of Sud-Chemie AG, Technical Information Department, TIXOTON CV 15, pp. 1-3, the bentonite being used in amounts of 17.5%.
The purpose of the invention is to provide supplementary agents or mixtures thereof for mineral binding systems in a form which enables easy and homogeneous mixing of even the smallest quantities with the fewest possible number of mixing operations in the production of the binder systems. Furthermore, the supplementing agent should not remain without effect in the system, like an inert filler, but rather improve the application properties of the finished system.